This invention relates to flame retardant polyolefin compositions. More particularly, this invention relates to flame retardant polyolefin compositions comprising polyolefin and a flame retarding amount of the pentate salt of an amino-s-triazine and to a method for rendering polyolefins flame retardant.
Polyolefins are difficult to render flame retardant. A number of halogen-containing flame retardants are known which, when compounded with polyolefins, provide non-burning compositions, i.e. materials which do not propagate flame. However, polyolefins such as polypropylene have a tendency toward dripping flaming drops which is quite difficult to overcome, and such non-burning compositions generally are not capable of being made fully self-extinguishing.
An alternative approach is to incorporate charforming additives which, in the presence of flame, form a thick, non-flammable insulating barrier to protect the substrate polymer. One such intumescent or char-forming system, disclosed in U.S. Pat. No. 3,936,416, employs a combination of melamine pyrophosphate and a polyol. This additive combination is effective in providing a non-burning, non-dripping polypropylene composition. Preparation and compounding with these materials can be difficult. During preparation, the additive combination must be degassed in order to avoid foaming during the compounding with polypropylene and/or in subsequent molding operations. In addition, the additive as obtained has a substantial tan or brown color which imparts an undesirable hue to the polypropylene composition, and the additive is obtained as a hard, solid mass which is pulverized with some difficulty for compounding.
An additive composition which has little or no foaming tendency at processing temperatures and which could be readily produced in usable form and without undesirable darker coloration would be a substantial advance over the presently available intumescent flame retardant additives for polyolefins.